I was in Toronto for a conference in 2003 and was shopping in Eaton Centre when I looked down and saw my phone was on. I shut it off, not thinking of anything. The next month, I get my phone bill to find 20 (long distance) calls to my parents number in Manitoba. I call SaskTel and get the charges reversed, thinking that this was a mistake and then phone my mom. Apparently I had pocket-dialed over and over again - scaring the crap out of my mom because my cell number wasn't coming up - she thought someone was stalking them.
I've pocket-dialed on my iPhone a few times too if I'm not careful after answering the phone - I find it usually goes back to the contacts list after phoning someone and I've found myself re-calling the same person I talked to.